This was a bit advanced than the previous workshop. The kids used an integrated circuit, the 555 timer. They learnt to operate it in both monostable and astable mode. In the monostable mode, a push button was used to turn an LED on, where as in astable mode, the circuit operated on its own.
Further more, some of them modified the astable circuit to alternatively blink two LEDs. A short video summary of the workshop is below: